Processor will underclock at low CPU usage with default bios settings. 8x to 6x etc.
To change this, under Advanced BIOS Features,
CPU Enhanced Halt (C1E) set to Disable
CPU EIST set to Diasable
Now your heat issue. You could have a HSF that is not properly seated. You should not be able to move the HSF assembly or lift it at any corner.
Did you apply a thermal compound between the CPU and HSF?
You should not have any problems with Q9550 /GA-P35-DS3L/F9c Bios.
For correct tempature readings use Speed Fan or Real Temp.
They are both free downloads.